update pixi env, try installing proj on macos ci (#271)

Author: wpbonelli

.github/workflows/ci.yml

@@ -80,9 +80,9 @@ jobs:
         with:
           repo: modflow6-nightly-build
 
-      - name: Install HDF5
+      - name: Install PROJ, HDF5, NetCDF (macOS)
         if: runner.os == 'macOS'
-        run: brew install hdf5
+        run: brew install proj hdf5 netcdf
 
       - name: Setup pixi
         uses: prefix-dev/[email protected]